The present invention relates to a handy rotary cutter of a type comprising a generally elongated handle and a disc blade rotatably carried by the handle at one end.
Various types of rotary cutters of the construction referred to above are well known. By way of example, U.S. Pat. No. 630,094, patented Aug. 1, 1899, discloses a rotary cutter which comprises a generally elongated handle, a stem member comprised of a pair of spaced plates of identical shape formed by folding a single metallic plate, such stem member being rigidly secured to one end of the handle and having a pair of spaced ear portions at a position opposite to the handle, a shaft having its opposed ends journalled by the ear portions, and a disc blade rigidly mounted on the shaft and positioned within the space between the spaced plates of the stem member.
A similar rotary cutter is also disclosed in U.S. Pat. No. 2,677,180, patented May 4, 1954. However, because of a limited field of application, the rotary cutter of the second mentioned U.S. patent further comprises a roller of generally truncated conical configuration rotatably mounted on the shaft between one of the ear portions and the disc blade for the purpose of preventing any possible penetration of the blade into the underlying wall when a web of paper adhering to the underlying wall is being cut.
Both of these conventional rotary cutters involve some common disadvantages. Specifically, even when the rotary cutter is not in use, the peripheral knife edge of the rotary blade is exposed to the outside and, therefore, the rotary cutter lacks a sufficient safety factor. In addition, since the disc blade is freely rotatable, the user or operator of the rotary cutter has to adjust the amount of a cutting force to be applied through the cutter to a material to be cut during the cutting operation and, at the same time, to adjust or control carefully the direction in which the cutting is to be performed. Unless care is taken in adjusting the amount of the cutting force and the cutting direction, the disc blade often runs over the material to be cut independently of the user's will even when a slight force is applied to the disc blade through the handle, resulting in a possible excessive cutting and/or damage to an area of the material not to be cut.
In general, with the prior art rotary cutters referred to above, due to the careful adjustment of the cutting force and the cutting direction required, a relatively large force is required to perform the cutting operation. This is particularly true when the cutting operation is performed subject to the material being placed on a hard, substantially polished support surface.
Although it does not appear to be pertinent to the present invention, the IBM Technical Disclosure Bulletin, Vol. 17, No. 10, March 1975, discloses a generally elongated handy safety knife comprising an elongated handle having one end to which a generally elongated knife blade is rigidly secured, a plate-shaped shaft having one end rotatably carrying a pair of guard rollers one on each side of the knife blade and the other end slidably housed within a slot in the handle, and a compression spring housed within the slot and interposed between the shaft and the handle for biasing the shaft in one direction to a projected position. In this safety knife, when the knife blade is applied to the material to be cut, the rollers are retracted against the biasing force of the compression spring to allow the tip of the knife blade to penetrate a predetermined distance into the material to be cut. When not in use, the rollers conceal the tip of the knife blade within the space between the rollers.
U.S. Pat. No. 4,020,550, patented May 3, 1977, the invention of which has been assigned to the assignee of the present invention, discloses the use of at least one elastic disc arranged in side-by-side relation to the disc blade and having a diameter larger than the diameter of the disc blade, a peripheral portion of the elastic disc being yieldable radially inwardly of the disc blade during the cutting operation to allow the peripheral knife blade to penetrate into the material to be cut. This U.S. patent also discloses the use of an adjustment mechanism for adjustably rotating the disc blade to enable different portions of the peripheral knife blade to be used at different times.